Metal forming



METAL FORMING Filed Feb. 23, 1960 3 Sheets-Sheet l #L W /y\ o m o O o O m l iii/a o O /7 IN V EN TOR.

4e THUR nae/.5

g- 1965 L. BALAMUTH ETAL METAL FORMING Filed Feb. 23. 1960 3 Sheets-Sheet 3 V/WX INVENTOR.

men/me Kale/s United States Patent Office 3,201,967 Patented Aug. 24, 1965 3,2ii1,%7 METAL FORMING Lewis Balamuth, Woodsitle, and Arthur Kuris, Riverdale, N.Y., 'assignors to Cavitron Ultrasonics Inc., Long Island, N.Y., a corporation of New York Filed Feb. 23, 196i), Ser. No. 10,280 2 Claims. (Cl. 72359) This invention relates generally to metal forming, and more particularly is directed to the provision of improved apparatus and methods for the forming or shaping of metals through the use of vibratory energy.

In existing methods and apparatus for forming metal, the metal to be shaped or formed is disposed between two cooperating die members having the desired contowards each other, and, even then, the existing methods and apparatus are not suitable for the forming or shaping of many metals which are either excessively brittle and thus tend to crack or exhibit surface failures at regions where they are sharply bent or made to How excessively, or where the metals suffer an undesirable decrease in strength as'a result of the heating required for the forming or shaping operation. The existing methods and apparatus for forming or shaping metals have the further disadvantage of limiting the shapes that can be formed, particularly with respect to the radii of curvature and the depth of the drawing of sheet metal formed thereby.

P Accordingly, it is an object of this invention to provide methods and apparatus for forming or shaping metals by the exertion of a relatively moderate pressure or force urging together the die members, and which can be practiced at room temperature.

A further object is to provide methods and apparatus for forming or shaping metals that are suitable for use in connection with metals or alloys that have heretofore either completely resisted, or presented severe difliculties in, the forming or shaping by conventional methods and apparatus.

Inaccordance with an aspect of the invention, die members are urged toward each other by a moderate static force with the metal to be shaped or formed positioned between the die members, and acoustic or ultrasonic vibrations are transmitted to at least one ofthe die members by wave motion through a solid transmitting .member or transformer, for example, at a frequency in the range between approximately 1 kc./sec. and 100 kc./ sec. and with a small amplitude, for example, in the range between approximately .01 inch and .0001 inch, in directions generally parallel to the static force. Preferably, the vibrations transmitted to the die member impart to the latter a peak acceleration of at least 1000 g. It has been found that the combined action of the vibratory energy and of the applied static force makes it possible to form or shape metals at room temperature with a relatively small applied static force, and further makes it possible to avoid the numerous defects and failures encountered when shaping or formingmetals by the pre- 'viously existing procedures, particularly when shaping or forming brittle materials. It appears that the vibratory energy exerts a kind of forging action on the metal being shaped and further drastically reduces the surface friction between the metal being shaped and the die mem bers. The reduction of surface friction facilitates flowing of the metal with respect to the active surfaces of the die members in order to permit the forming of relatively small radii of curvature and relatively deep drawing of the metal. Further, the reduction in the surface friction between the metal being formed and the die members by the action of the vibratory energy greatly facilitates the withdrawal of the formed article from the die members, and thereby permits the forming of articles with surfaces that may be practically parallel to the direction of separation of the die members.

In accordance with another aspect of the invention, the

vibratory energy transmitted to one or both of the die members is employed for heating the related die member so that the forming or shaping of the metal can be con veniently effected by the combined action of the static force urging the die members towards each other, the vibratory energy and the heating of one or both of the die members. 7 The above, and other objects, features and advantages of the invention, will be apparent in the following detailed description of illustrative embodiments thereof which is to be read in connection with the accompanying drawings forming apart hereof, and wherein:

FIG. 1 is a front elevational view, partly schematic and partly broken away and in section, of a metal forming apparatus embodying the present invention;

FIG. 2 is an enlarged axial sectional view of the die members included in the apparatus of FIG. 1, with such die members being spaced apart preparatory to the forming of sheet metal therewith;

FIG. 3 is an axial sectional view similar to a portion of FIG. 2, but showing the die members engaged during the forming of the metal sheet;

FIG. 4 is a View similar to FIG. 2, but showing a different arrangement of the die members;

FIG. 5 is a fragmentary elevational view similar to a portion of FIG. 1, but showing another embodiment of the invention, wherein both die members have vibratory energy transmitted thereto;

FIG. 6 is an enlarged fragmentary elevational view, partly in axial section, and illustrating a modified arrangement for supporting a vibrated die member .so that the transmission of vibrations to the latter will also efiect heating thereof;

FIG. 7 is an enlarged, axial sectional view similar to that of FIG. 3, but illustrating the application of this invention to the deep drawing of sheet metal;

FIGS. 8 and 9 are sectional views generally similar to those of FIGS. 2 and 3, respectively, but illustrating the application of this invention to the forming of solid metal articles from metal billets, rather than from sheet metal; and

FIG. 10 is a front elevational view of an apparatus constructed in accordance with still another embodiment of the invention.

Referring to the drawings in detail, and initially to FIGS. 1, 2 and 3 thereof, it will be seen that a metal forming or shaping apparatus embodying the present invention and generally identified by the reference numeral 10 includes die members 11 and 12 which are urged forcibly toward each other during the forming or shaping of metal therebetween, while vibratory energy is applied to one or both of the die members.

In the apparatus 10 illustrated in FIG. 1, the die members 11 and 12 are supported within a frame 13 that includesparallel uprights 14 and top and bottom cross members 15 and 16 suitably secured to the opposite ends of the uprights. Intermediate cross members 17 are secured, attheir opposite ends, to the uprights 14 at adjustably selected locations, for example, by pins 18 extending through openings in cross members 17 and through se- 1 1 i 3 lected Openings of a series of the uprights. a

A hydraulic cylinder 20, depends vertically between intermediate cross members 17 and has a mounting plate 7 21- atits upper end which is secured ,'as by bolts 22, to

the cross member-s17, and a vertically movablerrarnn23 projects upwardly .from cylinder opening in mounting plate 21. r f

Thedie member 12 is brazed;

extension 26 of the ram 23 (FIG. 2)'.so that the anvil 24 attachedto carrying the die member 121cm be' se curely the ram for'movement'with thelatter.i e 1 The other die member 11 is supported vertically above "die member 12 by avibratorymachine 27 that includes :an enclosure or casing'28 depending from amounting of openings 19 form'ed in each ZlLthr'Ough a suitable t V jsoldere d, or, otherwise rigidly attached to an anvil 24 having'a downwardly opening tapped bore or socket 25 for, receiving a threaded Ifro'mdist'ributor valve 45fbackitotank 43. Thus, in one I :position of the distributor valv'e 45,'hydraulic' fluid under 'pressure'is supplied through conduit 47 {to the'upper end of cylinder -20 to move the ram 23' downwardly, and

thereby space die irnember 12 from die member 11 so that metal to be formed-can be inserted between the die plate 29 secured, as by'bolts 30, to the top cross members 7 t 15. An acoustical impedance transformer 31has an en j larged cross sectional part intermediate its opposite ends defining a radial flange 32thatissecuredby' bolts133 to the, lower end of casing 28,.and a transducer 34ginthei form of a' stack of laminations of'magnetostrictive mate:

rial, for example, nickel or the like, isbraZ'edor soldered at one end to the end of transformer 31'withincasing 28 and is encircled by a Winding 35radapted to carryihighr'nernbers or. so that the formed-metal can be removed. Inthe other position" of valve 45,;l flexible conduit 1s connected to the return pipe'-4 9,,-while conduit 48 is connected to the outlet44 of pump g4l and lconveys hydraulic fluid u'n'der pressure tothe lower endg-ofcylinder 29' for urging die =member-l2 upwardly; toward the cooperating {dieir nembe r 11 which is simultaneouslyvibrated, as previoujsly indicated,rso that metaldisposed between the die members will be suitably formed or shaped by the combined raction of thestatidforce, which is represented by the arrow F (VFIG. 3) and which results'fror'n thehyamuse fluid under. pressure withiii cylinderr20, and of frequency current. Conductors extendtfrom winding35 a through a cable 36 to a suitabletgenerator, which is sche matically illustrated at 37. The generator 37 is eflfe'ctive totgenerate a high frequency current and a biasing direct current'which are supplied to thefcoilor winding 35', and the length of the transducer 34'isjso selected withireference to the desired frequency of vibrationsto be imparted the vibrations imparted to diemember liand represented bythe arrowsV. v V, 1 I

"Referring indetail to FIGS. 2 and 3, it will be seen that a the die members 11' and 12,,there illustratedareintended for dimpling sheet metal 50 around a hole 51-formed in the sheet metal so as' to receivethe countersunlg head of a-rivet orlother fastening and provide-aflujsh; surface.

tothe die member. 11 that the transducer will be resonant,

at such frequency and therefore standing waves will be set up therein with a loopbf motion'atleach end; For

an integral number of hal f'wave-lengths .ofsuch coma of the highfreq'uency current delivered to thewinding 35.

transformer 31' is securely "attached to 'a'tooliholder 38', for example, by forming the lowerjend ot-transformer r '31 with a threaded extension '39 which engages'in'atapped bore of the tool holder 381(FIG. 2), whilef the die a member l l'fis rigidly attached," for example, by brazing or soldering, to the lowerend of thetool holder.

this purpose, thelength ofjthe transducer 34 shou'ldib'e pressionalwaves induced by magnetostriction as a-resiilt 1 In the embodiment of the invention illustratedinFIGS.

For this,purpose,' die member 11;is'in thefo'rm of a male die member havinga pin 52 projecting axially therefrom to pass slidably throughthe hole 5 1]of thernetal sheet 50, and a flaring or frusto-conical portion 53 isfformed'at the base ofpin 52 and corresponds-tqthe shape of the ldimple to be formedaround the hole 51, -T he cooperating die lmember '12 isfin the fo'rm' of a female die member having a bore. 54 intended to slidably receive the pin SZ below the metal sheet 5 0jand: opening at itsupper end,

7 k I c 7 i into a'countersink'55f correspondingtothe shape of the 1, 2 and 3, the lower end of the acoustical l'irnpedance* J The transformer 31' is dimensionedjso as to eifect thev A desired amplification of the amplitude of the vibrations? transmitted thereto fromlthe transducer 34, and'the -over all length of] the transducer, transformer-31and tool holder 38Iis correlated to the frequency of-the compres sional waves generated by the transducer 34 s'o, that'a loop ofmotion occurs substantially at the diem'embeIT-I I'. 1 'For'the'purposesof the presentinvention, the frequency and amplitude of'the vibrations areselectedwsojas ,to give underside of sheet 5%) around the desired dimple;

i Thus, when. female die member 12 is urged toward male die member '11 by the static force Fwhile male die L nember ll'is vibrated, {'a s' represented by the arrows- V, 'jthe sheet; therebetween is formed-with'a dimple 56 aroundthe .openinglSl therein (FIG-3), '1 It has been foundthat, by nreason o f; the' vibratory energy imparted to die "member 11, the 'de'sired'dirnplei can besuitably zformed by. the exertion of a smaller static-force than that required v when the dimple is'formed merely ;by the "exertionfo f a static force, and that-the grain structure :of thefmetalf'sheet in the' areapf thedimple 56 is more desirablefinjthecaser'of the forming of the metal by the the vibrated diemember 'a peakl acceleration of at'least mately'l lee/sec. .to 100 kciQ/sec while thefamplitudefof the vibrations is within the range of approximately .0 li'nchf to .0001 inch. 1 i

' Thus, the die member of 'triwa paiaiasilo is stationaryandv has acoustical; or} ultrasonic vibratory energy imparted thereto by'the transmission of; al wave 10005 and the frequency; of thevibrations,imparted' to die member 11 maybewithinthelrange,of approxi- 60 fcombinedhaction of the statictforce and vibrations. For example, when formingdirnples' in 52 SO aluminum sheet "having a thickness of".032- inch,and employing an appa- 'ratus wherein the cylinder-"2 0 has a piston therein ,with

a diameter ofi inches, it was found that the static .force {resulting from a pressure *of; 50 pounds per-square, inch acting in said cylinder againstvth e pistongwas inadequate,

v by it'self, to lform va suitable dimple, whereas, that pressure 'was suflicienttd form an'acceptable; dimple when the force resultingftherefrom was combined with vibration of the die fine mb er' 1 1 at a j'ffrequeneyf of approximately 14 kc;/sec., and an .amplitude of vibration ofappioximately arrangement including a pump: 41;having ari inlet conduit v t 42 drawing hydraulic'fluid'l'froma supply 5111643 an T, anoutlet conduit 44 extendihgtr'om-thejuhip to adis-ff Further, it has; been; foundr'thatflthe combined static force and vibratorygenergyis'lsuitable for shaping (informing rnetals that cannot besatisfactprily.shaped or formed by, st ner me'n S. For; example, 7 a Lsheet AllOAT titaniumhaving a; thickness J,of ,025, inch was formed with inch dimpleusing a sta't" bined with vibrations a ing paw frequency im-0 o rce 500 pounds com .0007 inch, whereas an attempt to form a similar dimple in the same material using only a static force of 500 pounds resulted in visible cracking of the sheet material.

I Although FIGS. 2 and 3 of the drawings show the male die member or punch 11 attached to the vibrated tool holder 38 while the female die member 12 is attached to the anvil 24, it is apparent that the positions of the male and female die members can be reversed. Thus, as shown in FIG. 4, the male die member llla may be rigidly attached, as by soldering, brazing or the like, to the anvil 24 secured on the ram 23 of hydraulic cylinder 20, while I the female die member 12a is similarly attached to the tool holder 38 and has vibratory energy transmitted thereto from the vibratory machine 27. In fact, it has been found that, where only one of the die members is vibrated, the static force required for forming the metal is decreased if the single vibrated die member is the female die member, as in FIG. 4.

Further, although the die members illustrated in FIGS. 2 and 3 and in FIG. 4 are intended for forming relatively shallow dimples in sheet metal, it is to be noted that the present invention may be very advantageously applied to the deep drawing of sheet metal. Thus, as illustrated in FIG. 7, the female die member 12b mounted on the ram 23 of the hydraulic cylinder is formed with a relatively deep, suitably shaped cavity 57, while the vibrated male die member 11b secured to the threaded extension 39 of the transformer 31 of vibrating machine 27 is formed with a projection 58 having a contour corresponding to that of the cavity 57, whereby the die members 11b and 12b will cooperate, upon the application of a suitable static force and vibrations, to form a deep draw of the metal sheet 50b within the cavity 57. By reason of the vibrations imparted to the die member 11b and the consequent reduction of surface friction, flowing of the metal within the cavity 57 is promoted to permit deep drawing of the sheet metal without the danger of tearing thereof, and further the reduced surface friction between the sheet metal and the active surfaces of the die members greatly facilitates the withdrawal of the formed sheet metal from engagement with the die members.

Although the previously described embodiments of the invention have related to the shaping or forming of sheet metal, it is to be noted that the invention can also be advantageously applied to the shaping or forming of solid metal articles. Thus, as illustrated in FIGS. 8 and 9, both of the die members 110 and 120 rigidly secured to the tool holder 38 and the anvil 24, respectively, may be formed with cooperating cavities 59 and 60 so that, when a billet ties 59 and 6t) cooperating to define an article 62 (FIG. 9)

of the desired shape. By reason of the vibrations imparted to the die member 110, surface friction between the formed article and the active surfaces of the die members is substantially reduced, and the formed article 62 can be easily removed from the die cavities upon separation of the die members, whereupon the flashing 63 which occurs at the line of separation of the two die cavities 59 and 60 can be easily ground away.

It is also apparent that only one of the die members may have a cavity or depression therein, while the other die member is in the form of a flat platen or anvil.

Although the above described embodiments of the invention have imparted vibratory energy only to one of the cooperating die members, it is to be understood that, in each case, the invention contemplates the vibrating of one or both of the die members. Accordingly as illustrated in FIG. 5, the ram 23 of the hydraulic cylinder may carry a vibrating machine 27 which is similar to the previously described vibrating machine 27 and which includes an acoustical impedance transformer 31' having a tool holder 38' rigidly attached thereto and carrying the die member 12 so that, while die member 11 is vibrated by operation of the vibrating machine 27, the other die member 12 is simultaneously vibrated by operation of the vibrating machine 27'.

Thus, in the arrangement of FIG. 5, both of the die members 11 and 12 are simultaneously vibrated either in phase with each other or with the respective vibrations being varying degrees out of phase with respect to each other, either at the same frequency or at different frequencies effective to produce beats, and at the same amplitude or at different amplitudes, while such die members are forcibly urged together in order to effect the efiicient forming of metal disposed therebetween.

In the previously described mbodiments of the invention, the vibrated die member :has been rigidly attached to the tool holder, and the latter has, in turn, been rigidly attached to the impedance transformer of the vibrating machine, thereby to avoid the generation of heat at the several joints. Although the present invention makes possible the forming of metals at room temperature by the combined action of a static force and vibrations, it may be desirable in some circumstances .to either heat the metal to be formed or to apply heat to the metal during the shaping or forming thereof. The fact that vibratory energy is effective to generate heat when it is transmitted through a loose joint makes it possible to effect heating of the metal during the forming or shaping thereof through conversion of some of the transmitted vibratory energy into heat, thereby to avoid the necessity of using the convention-a1 electrical heating elements frequently provided in metal forming apparatus. As shown in FIG. 6, the vibrating machine 27d, which is generally similar to the vibrating machine 27 described in connection with FIG. 1, has an acoustical impedance transformer 31d which is formed with a smooth, reduced diameter extension 39d in place of the threaded extension 39 of the first described embodiment. Further, the tool holder 38d having the die member =1-1d rigidly attached to its lower end, as by brazing, soldering or the like, is formed with a smooth, upwardly opening axial bore 40d adapted to slidably receive the extension 39d. The tool holder 38d is frictionally held upon the extension 39d by a spring circlet or split ring .64 received in an annular groove 65 formed in the surface of extension 39d and bearing radially outward against the surface of bore 40d.

By reason of the frictional attachment of the tool holder 38d to the extension 3d of transformer 31d, the acoustical or ultrasonic vibrations being transmitted from the transformer to the tool holder produce considerable frictional heating at the joint and such frictional heating is transmitted, along with the vibrations, to the die member 1103.- Although FIG; 6 illustrates a connection for the die member 11d that is effective to produce heating of the latter, it is apparent that a similar connection may be provided for the other cooperating die member when the latter is also vibrated in order to achieve heating of both die members.

In FIG. 1, and in the other embodiments of the invention that have been described, it has been assumed that the static force cooperating with the vibrations to effect the forming or shaping of the metal has been applied by a hydraulically operated cylinder, for example, the cylinder 20 of FIG. 1. However, the static force may be otherwise applied, for example, as in the apparatus 102 illustrated in FIG. 10, where the lower die member is stationary and the upper die member is urged downwardly by the force of gravity.

In the apparatus 10e, the frame .132 once again includes.

uprights 14s and top and bottom cross members 15a and Me. The intermediate cross members 17e are fixedly attached, at its opposite ends, to the uprights 14c, and the upper die member 11a is secured-to the lower'e nd of the tool holder 38a which is rigidly attached to theacoustical impedance transformer 31a of the vibrating machine 27c depending from a mounting rplate 29:2, and the latter is sec red, as by -bolts 30e to a vertically 'movablecross head 66; The vertical movements of the cross head 66 may be guided by rollers :61 at the opposite ends'thereo'f engaging'flanges of the uprights 142, and the desired downward force for urging the die members 11 e and 12a towards each other may be achievedby providing a suitwith an acceleration far less than said peak accelerations so that saidfstatic force and the impacts resulting from said vibrations combine to form metal disposed between said surfaces ofgt-he'die members to the configuration of the latter while said peak accelerations ensure that at least the metal forming surface of saidonedie member is only in intermit tent and relatively movable contact with the metal" to very substantially reduce the frictional resist-j ance to forming of the metal. I v I 2. An apparatus-for ldirnpling a metal sheet around a hole. in;the latter, comprising male and'female die members respectively having convex and concave mating frustoconicalsurfacesengageable with'the opposite sides able weight or weights/68 on the cross head66. Thus,

in FIG. l0,' th'e static force combining with'the vibrations to form or shape the metalbetwe'en the die' members is represented by theforce of gravity acting on the assembly 7,

of the cross head'66,-weight"or weights 68'and' thevilbratingmaohinezTe. V 3 Suitable means is also preferablyfprovided for elevating the cross head tie' whenmeta'l is' -'to be inserted, or rernoved from, between ithe jdie' 'rne'nrbers'.v -A suitable mechanism for that bur-pose is schematically illustrated in FIG. and includes cables f69 extending upwardly from the cross Head over pulleys 7 0 rotatably' mounted' on the top'cross member e, and then-:runningovera' double pulley 7-2 rotatably mounted at the' upperjend o f one'ofthe uprights 142 beforebeing taken upon a winch 72, "It 'will be understood th at,-, duri n'g the forming or shaping ofi metal betweenith'e diemembers lle'iand'll,

the winch*72 is manipulated to permit loweringof (cross 5 head 66 and to provide slack in the eables'69 whenthe die members engage the metal there-between so 'thatthe full weight of the vertically movable assembly can actrto provide the desired static force;

invention is notlimited'to fthojse ,pre'cise embodiments,- and t-hat'varions changes and modifications may beeffected therein without departing from the scope or spirit of the invention, except as definedin-the appended claims, whatisclaimedisz' ltho ugh 'illustrativeembodiments of the invention have beendescribed in detail he'rein'with reference to the accompanying-jdrawings, it is to be understood that-the r 1. 'Meta1 forming-apparatus'compi'isingtwddk meni ,7

Peers movable ,rectilinearly toward and away from each other and having cooperative-"metal forming surfaces. which, forthe most part, are atsubstantialangles with respect to the direction ofthe relative movement of the I die members,m'eans' applying vibrations to..at least one of said die}members'substantially at-the center'thereof and in directions parallel to thedirectio'n in'which said die members are movable towardgand'away from each ot-her,

said vibrationsbeing at a frequency in the range between approximately 1 kc./ sec. andrlOQ kcJsec. andan amplif tude-suflicient to ir'n-partpeak --acc'elerations of atflleast 10 00 g..to t-he' related die memben'and meansexertin'g a static force :ur-gin'g said di e niembers toward each' -other eluding a magnetostrictive transducer extending parallel.

to the direction of said'relative movement and being centred, transversely relative tofsaid direction, with respect to said one-die member, c'onnectingmeans --exte'nding longitudinally frornfone endof said transducer t-o said Y one, die memben-means establishing a high frequency, biased -alternating, field aroundsaidtransducer so that the'latter-produceslongitudinal vibrations at a; corresponding frequency transmitted 'to' said one die member through said connecting means and hav'in'ga loop of longitudinal motion substantially at said one die member, 1 and a supporting stnucture secured'to saidconnecting meanssubstantially'at'a node of the longitudinal-motion thereinjsaid frequency of the vibrations being in the range between 1 kc./ sec.'a'nd-l00 kc./see. and the vibrations havin'g an amplitude sufficient toimp-art peak accelerations of atleast 1000--g to the, relate ddie member; and 'm'eans exertin-g astatic force by way of said supporting means for urging said die members toward each other with an acceleration afar less'th-an said peak accelerations so that at least said-one die member is only'in intermittent and hammering contact, at said frequency,- with'a metal sheet placed between said'die members. a

Q References tlitedby the lilxaminer J f UNITED STATES PATENTS 1,502,722 7/24 Hill 78-60 1,706,370' 3/ 29 Woodings 78-60 2,382,045 8/45 Flowers 29-552 2,393,131 1/46- Vang; a

7' 2,441,517 "5/48 ,Sussman.

2,569,226 [9/51 Carter; 25-41 2,709,933- 6/55 Reed 29-552 2,815,535 1-2/ 57, 'Bodine 1 25-41 3,002,614-3.10/61' Jones. a

5w. ANHAM, fPrim izry real- .WHITMORE'A.-WILTZ, HYLAND BIZOT, WILLIAM L STBPHENSON,Examiners. a 

1. METAL FORMING APPARATUS COMPRISING TWO DIE MEMBERS MOVABLE RECTILINEARLY TOWARD AND AWAY FROM EACH OTHER AND HAVING COOPEATIVE METAL FORMING SURFACES WHICH, FOR THE MOST PART, ARE AT SUBSTANTIAL ANGLES WITH RESPECT TO THE DIRECTION OF THE RELATIVE MOVEMENT OF THE DIE MEMBERS, MEANS APPLYING VIBRATIONS TO AT LEAST ONE OF SAID DIE MEMBERS SUBSTANTIALLY AT THE CENTER THEREOF AND IN DIRECTIONS PARALLEL TO THE DIRECTION IN WHICH SAID DIE MEMBERS ARE MOVABLE TOWARD AND AWAY FROM EACH OTHER, SAID VIBRATIONS BEING AT A FREQUENCY IN THE RANGE BETWEEN APPROXIMATELY 1 KC./SEC. AND 100 KC./SEC. AND AN AMPLITUDE SUFFICIENT TO IMPART PEAK ACCELERATIONS OF AT LEAST 1000 G. TO THE RELATED DIE MEMBER, AND MEANS EXERTING A STATIC FORCE URGING SAIS DIE MEMBERS TOWARD EACH OTHER WITH AN ACCELERATION FAR LESS THAN SAID PEAK ACCELERATIONS SO THAT SAID STATIC FORCE AND THE IMPCTS RESULTING FROM SAID SURFACES OF THE DIE MEMBERS TO THE CONFIGURATION OF THE LATTER WHILE SAID PEAK ACCELERATION ENSURE THAT AT LEAST THE METAL FORMING SURFACE OF SAID ONE DIE MEMBER IS ONLY IN INTERMITTENT AND RELATIVELY MOVABLE CONTACT WITH THE METAL TO VERY SUBSTANTIALLY REDUCE THE FRICTIONAL RESISTANCE TO FORMING OF THE METAL. 